Sometimes these things happen. I have had it happen. Sometimes you make a good shot & it gets deflected and perhaps we sometimes take an inappropriate shot.Deer was quartering away hit back ham and gut. Best l can tell he had buck fever and pulled. 50 cal. Hornady FPB 300 gr. with 90 grains of triple 7.
I say analyze and learn from it. Don't obsess about it but self study. Help that amazing young man grow and become a better hunter. Not saying what happened was bad or he did bad. Great time to reflect and grow. Learn to not shot through brush but through holes in brush. Learn to respect the shot and make the shot, to wait for the shot or pass if necessary. Learn to minimize waste in the future then the great buck he killed was still of great value.
Make it positive but acknowledge the negative.
Respectfully